1. Field of the Invention
The present invention relates to an endless belt for feeding paper to a printer in an apparatus for feeding paper to printers used in computers, word processors, plotters, etc. as well as various other printers.
2. Description of the Prior Art
As paper for recording characters and graphics which are printed from printers used in computers, word processors, plotters, etc., there is used in many cases paper having a single row of feed holes formed in each of both side portions of the paper. The feed holes are formed at equal intervals on straight lines extending along both side edges of the paper in positions spaced a predetermined distance from the side edges.
In an apparatus for feeding this kind of paper to a printer, a pair of endless belts are disposed along the feed path of paper to be fed to the printer, in positions corresponding to both side portions of the paper. On each of the endless belts are formed a large number of feed pins in a single row at the same intervals as those of the feed holes formed in the paper. The endless belt is interconnected between a driving pulley and a driven pulley or a belt guide member. When the driving pulley is rotated, a plurality of feed pins located on the rectilinear portion of the endless belt between the driving pulley and the driven pulley or the belt guide member come into engagement with feed holes formed in the paper, thereby feeding the paper to the printer.
Generally speaking, in order to facilitate the insertion of the feed pins formed on the endless belt into the feed holes formed in paper, the outer peripheral surface of each feed pin is in the form of a truncated cone having a conical peripheral surface formed as a curved surface somewhat expanding outwards. Further, in order for the engaged pins to be easily disengaged from the feed holes, the outside diameter of the portion of each feed pin which portion comes into engagement with a feed hole is set a little smaller than the diameter of the feed hole.
During printing of characters or graphics on paper in a printer, the endless belts sometimes repeat their forward and backward movements to move the paper forward and backward repeatedly. For moving the paper forward, as shown in FIG. 5, the outer peripheral portions on the front side in the feed direction of feed pins 7 provided on a rectilinear portion 4 of an endless belt 1 come into abutment with the edge portions on the front side in the feed direction of feed holes 13 formed in paper 12, whereby the paper 12 is moved forward. On the other hand, for moving the paper backward, as shown in FIG. 6, the outer peripheral portion on the rear side with respect to the feed direction of the feed pins 7 come into abutment with the edge portions on the rear side with respect to the feed direction of the feed holes 13 formed in the paper 12, whereby the paper is moved backward. In such a structure, when forward and backward movements of the endless belt 1 are repeated, the amount of forward feed and that of backward feed of the paper 12 are sometimes not coincident with those of the endless belt 1 due to gaps formed between the outer peripheral surfaces of the feed pins 7 and the peripheral edges of the feed holes 13, resulting in that characters or graphics to be printed are not printed accurately.